Transcript Mendel`s Laws of Heredity

Mendel’s Laws of
Heredity
Why we look the way
we look...
Father of Modern Genetics
Gregor Mendel
Born in 1822
Studied science,
mathematics and statistics
Entered an Austrian
monastery to be a monk
Studied heredity in peas
Discovered the principles
of heredity
What is heredity?
The
passing on of
characteristics (traits)
from parents to offspring
Genetics is the study of
heredity
Mendel used peas...
They
reproduce sexually
They have two distinct,
male and female, sex cells
called gametes
Their traits are easy to
isolate
Mendel crossed them
Fertilization
- the uniting
of male and female
gametes
Cross - combining gametes
from parents with
different traits
Mendel’s Peas

These are the seven characteristics, each having two contrasting traits, that
Mendel identified.
Questions
What
What
What
What
What
What
did Mendel cross?
are traits?
are gametes?
is fertilization?
is heredity?
is genetics?
What Did Mendel Find?
He
discovered different
laws and rules that explain
factors affecting heredity.
Rule of Unit Factors
Each
organism has two
alleles for each trait
–Alleles - different forms of
the same gene
–Genes - located on
chromosomes, they control
how an organism develops
Rule of Dominance
The
trait that is observed
in the offspring is the
dominant trait (uppercase)
The trait that disappears
in the offspring is the
recessive trait (lowercase)
Law of Segregation
The
two alleles for a trait
must separate when
gametes are formed
A parent randomly passes
only one allele for each
trait to each offspring
Law of Independent
Assortment
The
genes for different
traits are inherited
independently of each
other.
Questions...
How
many alleles are there
for each trait?
What is an allele?
How many alleles does a
parent pass on to each
offspring for each trait
Questions...
What
do we call the trait
that is observed?
What case (upper or lower)
is it written in?
What about the one that
disappears?
What case is it written in?
Phenotype & Genotype
Phenotype
- the way an
organism looks
– red hair or brown hair
genotype
- the gene
combination of an organism
– AA or Aa or aa
Heterozygous & Homozygous
Heterozygous
- if the two
alleles for a trait are
different (Aa)
Homozygous
- if the two
alleles for a trait are the
same (AA or aa)
Dihybrid vs Monohybrid
 Dihybrid
Cross - crossing parents who
differ in two traits (AAEE with aaee)
 Monohybrid Cross - crossing parents
who differ in only one trait (AA with
aa)
Questions...
What
is the phenotype?
What is the genotype?
What is homozygous?
What is heterozygous?
What is monohybrid
crossing?